For many years diazotype compositions have included, in addition to the primary light sensitive diazonium salt component and azo coupler component, various adjuncts such as acidifiers, solubilizers, and stabilizers. Among these latter adjunct materials, thiourea has proved to be extremely versatile in stabilizing coating compositions and coated materials alike; to the extent, in fact, that it is utilized as a universal component in diazotype compositions.
More recently, however, thiourea and its use in numerous compositions, including diazotype formulations, has gained notoriety and come under the scrutiny of health and environmental agencies. As a result, there exists a definite danger that the continuation of this otherwise beneficial use of thiourea may be severely limited if not entirely curtailed. A substitute compound with the broad stabilizing utility of thiourea is thus clearly needed.